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United States Patent Application |
20120011950
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Kind Code
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A1
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Kracke; Jeremy Alan George
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January 19, 2012
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Actuator Arrangement
Abstract
An actuator arrangement comprises a carriage secured to a nut of a ball
screw actuator, a support member, and bearing means whereby the carriage
is supported for axial movement relative to the support member.
Inventors: |
Kracke; Jeremy Alan George; (Stone, GB)
|
Assignee: |
Goodrich Actuation Systems Limited
Solihull
GB
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Serial No.:
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900716 |
Series Code:
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12
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Filed:
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October 8, 2010 |
Current U.S. Class: |
74/89.23 |
Class at Publication: |
74/89.23 |
International Class: |
F16H 25/12 20060101 F16H025/12 |
Foreign Application Data
Date | Code | Application Number |
Oct 9, 2009 | GB | 0917693.4 |
Jun 11, 2010 | GB | 1009742.6 |
Claims
1. An actuator arrangement comprising a carriage secured to a nut of a
ball screw actuator, a support member, and bearing means whereby the
carriage is supported for axial movement relative to the support member.
2. An arrangement according to claim 1, wherein the support member is of
cylindrical or part cylindrical form, the carriage bearing upon the
support member.
3. An arrangement according to claim 1, wherein the carriage is located
within the support member.
4. An arrangement according to claim 1, wherein the support member is of
elongate, generally tubular form, the nut of the ball screw actuator
being located within the support member and the carriage being external
of the support member, the carriage and nut being secured to one another
by a fastener means that extends through a slot provided in the support
member such that the fastener means moves along the slot as the nut and
carriage are driven for movement.
5. An arrangement according to claim 1, wherein the bearing means
comprise a sliding bearing.
6. An arrangement according to claim 1, wherein the bearing means
comprise a series of wheels, rollers, balls or other bearing elements
mounted upon the carriage and arranged to be conveyed upon or within the
support member.
7. An arrangement according to claim 1, wherein the support member is
provided with guide means with which the bearing means cooperate.
8. An arrangement according to claim 7, wherein the guide means is in the
form of one or more elongate guide grooves.
9. An arrangement according to claim 1, further comprising a housing
permitting rotary motion of a screw shaft of the ball screw actuator, the
support member being angularly moveable relative to the housing.
10. An arrangement according to claim 9, wherein a sliding bearing is
provided to sustain the support member for such angular movement.
11. An arrangement according to claim 10, wherein a further sliding
bearing is provided between the nut and/or carriage and the support
member.
Description
[0001] This invention relates to an actuator arrangement, and in
particular to an actuator arrangement suitable for use in driving a
leading edge slat or other aircraft flight control surface for movement.
However, it may be used in other applications.
[0002] It is known to provide an aircraft wing with leading edge slats
which can be moved to a position ahead of the remainder of the wing
structure in order to modify the aerodynamic properties of the aircraft
wing. By moving the leading edge slat forwardly of the remainder of the
wing by a distance sufficient to open a slot in the overall wing profile
through which air flow can take place, allowing air to flow from beneath
the wing to the upper surface thereof, the angle of attack of the wing
can be modified, for a given air speed, thereby allowing adjustments in
the level of lift that can be achieved.
[0003] Typically the slats are driven for movement using curved racks
which are driven for movement by the rotation of pinions driven from a
drive shaft. However, such arrangements have the disadvantage that they
are not particularly compact, and often place design constraints upon
other parts of the aircraft wing, for example requiring the formation of
openings in the front spar of the wing through which the racks can extend
when retracted.
[0004] Copending British Patent Application no 0911733.4 describes an
actuator arrangement in which, rather than using curved racks, a scissor
linkage arrangement is used to drive the leading edge slats for movement.
The scissor linkage arrangement includes an actuator arm pivotally
mounted to a carriage and arranged such that axial movement of the
carriage, and hence translational movement of the point at which the
actuator arm is connected to the carriage, causes extension or retraction
of the scissor linkage. The nature of the scissor linkage is such that,
during axial movement of the carriage, angular movement thereof also
takes place, the scissor linkage allowing the associated slat to move
through an arcuate path of movement.
[0005] The carriage is mounted upon the nut of a ball screw type actuator
arranged such that rotation of a screw shaft of the actuator whilst
significant rotation of the nut is resisted results in translation of the
nut, and hence of the carriage secured thereto. It will thus be
appreciated that rotation of the screw shaft results in deployment or
retraction of the leading edge slat.
[0006] As a large proportion of the loads to which the leading edge slat
is subject, in use, are borne by the actuator arm, and so are transmitted
to the carriage, it is important to ensure that the carriage is
adequately supported in order to ensure that these loads can be fully
accommodated. Without appropriate support, the applied bending moment
could cause distortion of the carriage, or misalignment of parts of the
associated actuator, which could result in jamming of the actuator and
leading edge slat.
[0007] It is an object of the invention to provide an actuator arrangement
suitable for use in such applications, whereby the carriage can be
adequately supported.
[0008] According to the present invention there is provided an actuator
arrangement comprising a carriage secured to a nut of a ball screw
actuator, a support member, and bearing means whereby the carriage is
supported for axial movement relative to the support member.
[0009] The support member is preferably of cylindrical or part cylindrical
form, the carriage bearing upon the support member. Alternatively, the
carriage may be located within the support member.
[0010] The support member is conveniently of elongate, generally tubular
form, the nut of the ball screw actuator being located within the support
member and the carriage being external of the support member, the
carriage and nut being secured to one another by a fastening that extends
through a slot provided in the support member such that the fastening
moves along the slot as the nut and carriage are driven for movement.
[0011] The bearing means may comprise a sliding bearing. Alternatively,
the bearing means may comprise a series of wheels, rollers, balls or
other bearing elements mounted upon the carriage and arranged to be
conveyed upon or within the support member.
[0012] As mentioned hereinbefore, the carriage may be provided with
bearing means, preferably ball or roller bearing means, cooperable with
the support member such that the carriage is supported by the support
member. Conveniently, the support member is provided with guide means,
for example in the form of guide recesses, with which the bearing means
cooperate.
[0013] The actuator arrangement conveniently further comprises a housing
rotatably supporting a screw shaft of the ball screw actuator, the
support member preferably being angularly moveable relative to the
housing. A sliding bearing is preferably provided to sustain or support
the support member for such angular movement.
[0014] Another sliding bearing is preferably provided between the nut
and/or carriage and the support member. It will thus be appreciated that
good bearing for the support member is provided, and consequently that
the carriage is well supported and thus able to bear the loads applied
thereto, in use.
[0015] As mentioned hereinbefore, the ball screw actuator preferably
includes a screw shaft. The screw shaft may be driven by a drive shaft
which extends within the support member. However, this need not always be
the case and arrangements are possible in which the drive shaft does not
extend within the support member. The drive shaft preferably extends to a
position in which it can be connected to the drive shaft of another
similar actuator arrangement.
[0016] It will be appreciated that the actuator arrangement is
advantageous in that it permits support of the carriage, and hence of an
actuator arm secured thereto, in a relatively simple and convenient
manner, the actuator arrangement being of relatively compact form, and
hence of a form suitable for use in the confined space in the leading
edge structure of an aircraft wing.
[0017] The invention will further be described, by way of example, with
reference to the accompanying drawings, in which:
[0018] FIG. 1 is a view illustrating a scissor linkage being used in
controlling the movement of a leading edge slat;
[0019] FIG. 2 is a sectional view of an actuator arrangement in accordance
with an embodiment of the invention and suitable for use in driving the
scissor linkage for movement;
[0020] FIG. 3 is a diagrammatic representation of an alternative scheme;
[0021] FIGS. 4 and 5 are views illustrating two implementations of the
scheme of FIG. 3;
[0022] FIG. 6 is a part sectional view illustrating part of an actuator
arrangement in accordance with another, preferred, embodiment of the
invention; and
[0023] FIG. 7 is a view illustrating part of the actuator arrangement of
FIG. 6 in greater detail.
[0024] Referring firstly to FIG. 1 there is illustrated a scissor linkage
arrangement 10 for use in driving a leading edge slat 12 for movement
relative to the main wing structure 14 of an aircraft wing. In the
position illustrated, the scissor linkage arrangement 10 is in an
intermediate position between its stowed and fully deployed positions.
[0025] The scissor linkage arrangement 10 comprises an actuator arm 16
pivotally mounted, at one end thereof, to a mounting bracket associated
with the leading edge slat 12, and pivotally connected at its opposite
end to an axially translatable, and angularly moveable, carriage 18. The
carriage 18 is arranged to be driven for axial movement by an appropriate
drive mechanism (not shown in FIG. 1).
[0026] A support arm 20 is pivotally mounted, at one end, to the main wing
structure 14, the other end of the support arm 20 being coupled to an
intermediate part of the actuator arm 16 by a coupling which permits
three degrees of relative motion therebetween.
[0027] A scissor linkage of this type is described in greater detail in
copending application number GB0911733.4.
[0028] In use, axial displacement of the carriage 18 moves the point at
which the actuator arm 16 is pivotally connected to the carriage 18
either closer to or further away from the point at which the support arm
20 is pivotally connected to the main wing structure, depending upon the
direction of movement of the carriage 18. As a result, the scissor
linkage 10 operates to drive the leading edge slat 12 between its stowed
and fully deployed position. As described in GB0911733.4, the pivot axis
of the support arm 20 is defined, relative to the axis of movement of the
carriage 18, to result in the leading edge slat following a desired
curved path of movement as it is driven between its stowed and fully
deployed positions.
[0029] It will be appreciated that, in use, significant loadings are
transmitted through the scissor linkage 10 as the scissor linkage 10 has
to fully support the weight of the leading edge slat 12 and, more
importantly, react the aerodynamic loadings thereon. Although the pivotal
mounting of the support arm 20 to the main wing structure 14 can
reasonably easily be designed in such a manner as to be able to withstand
and bear such loadings, supporting the carriage 18 in such a manner as to
be able to bear such loadings, whilst being able to transmit drive to the
carriage 18 to move the carriage 18 in the axial direction in order to
drive the scissor linkage 10, and hence the leading edge slat 12, for
movement, is more difficult.
[0030] In accordance with one embodiment of the invention, as shown in
FIG. 2, an actuator arrangement 22 is provided to transmit axial drive to
the carriage 18 whilst providing adequate support thereto.
[0031] The actuator arrangement shown in FIG. 2 comprises a housing 30
adapted to be secured, by mountings 32, to parts of the main wing
structure 14. The housing 30 supports a drive shaft 34 for rotation
relative thereto by means of bearings 36. A torque limiter 38 couples the
drive shaft 34 to a drive transmission tube 40, whereby rotary drive from
the drive shaft 34 is transmitted to a screw shaft 42 of a recirculating
ball screw actuator 44. The free end of the screw shaft 42 is coupled to
the drive shaft 34 by a backlash coupling 46. In normal use, the backlash
coupling 46 does not transmit drive between the drive shaft 34 and the
screw shaft 42, drive being transmitted via the torque limiter 38 and
drive transmission tube 40, but in the event of relative movement
occurring between the drive shaft 34 and the drive transmission tube 40,
for example as a result of a failure in the torque limiter 38, then drive
can be transmitted through the backlash coupling 46 once the backlash
therein has been taken up.
[0032] The ball screw actuator 44 further includes a nut 48 coupled to the
screw shaft 42, the coupling being such that, upon rotation of the drive
shaft 34 and screw shaft 42, the nut 48, which in use is restrained
against significant angular movement by its connection to the actuator
arm 16 (described below) is driven for axial movement.
[0033] The nut 48 is coupled to the carriage 18 which is in the form of a
tubular shaft 50 carrying, at its end remote from the nut 48, a bracket
52 to which the actuator arm 16 is pivotally mounted, in use.
[0034] At its end adjacent the bracket 52, the carriage 18 is provided
with a sliding bearing 54 whereby the carriage 18 is supported for axial,
sliding movement upon support means in the form of a tubular extension 56
of the housing 30. As the sliding bearing 54 is aligned with or close to
the point at which the actuator arm 16 is pivotally connected to the
carriage 18, it will be appreciated that the applied loadings can be
efficiently transmitted to the support means with minimal distortion of
the carriage 18, the application of bending moments thereto being avoided
or very significantly reduced. The end of the tubular extension 56 of the
housing 30 adjacent the point at which the drive transmission tube 40 is
attached to the screw shaft 42 also carries a sliding bearing 58 which
further serves to support the carriage 18. A further sliding bearing 60
is secured to a fixed part (not shown) of the main wing structure 14 also
adjacent the point at which the drive transmission tube 40 is attached to
the screw shaft 42 and, again, serves to support the carriage 18. It will
be appreciated that the various sliding bearings serve to fully support
the carriage for axial, and limited angular, movement, thereby ensuring
that loadings transmitted thereto from the actuator arm 16 can be reacted
to the main wing structure 14, either directly or via the housing 30.
[0035] In use, several actuator arrangements of this type will typically
be arranged in an end to end configuration, and it will be appreciated
that the drive shafts 34 thereof can be interconnected with one another
such that a single drive motor (not shown) can be used to drive the
carriages 18 of each actuator arrangement for movement.
[0036] FIG. 3 illustrates, diagrammatically, a variant in which the drive
shaft 34, rather than extending through the housing 30, is spaced
therefrom, and a suitable drive transmission 34a, optionally including a
no-back device, is provided to transmit drive to the screw shaft 42 of
each actuator 44. The nut 48 of each actuator 44 is rigidly connected to
the associate carriage 18, thus each actuator 44 serves to drive the
associated carriage 18 for axial movement. In accordance with the
invention, support means 56a sustains the carriage 18 for sliding
movement. As with the arrangement of FIG. 2, the support means 56a is
aligned with or located adjacent or close to the point at which the
actuator arm 16 is connected to the carriage 18, thereby ensuring that
the loads can be reacted without significant distortion or misalignment
occurring.
[0037] As shown in FIG. 4, the support means 56a may comprise a member 62
defining a part cylindrical recess 64 within which the carriage 18 can
ride, the carriage being sustained for sliding movement within the recess
64 by wheels, rollers, balls or other bearing elements 66 incorporated
into the design of the carriage 18. Alternatively, as shown in FIG. 5, a
member 62a having a part cylindrical outer periphery may be provided,
upon which the carriage 18 is sustained and guided for movement. Again,
wheels, rollers, balls or other bearing elements 66 may be incorporated
into the design of the carriage 18 to provide a bearing between the
carriage 18 and the support member 62a.
[0038] Referring next to FIGS. 6 and 7 of the accompanying drawings, a
currently preferred form of actuator arrangement comprises a ball screw
actuator 110 having a rotatable screw shaft 112 with threads that
cooperate with ball components (not shown) associated with a nut 114. The
shaft 112 is coupled via a torque limiting connection or torque limiter
116 to a drive input 118 supported for rotation relative to a housing 120
by bearings 122.
[0039] A tubular support member 124 encircles the screw shaft 112 and an
end of the support member 124 projects into the housing 120 where the end
part of the support member 124 is sustained via slide bearings (not
shown) so as to permit the support member 124 to move angularly relative
to the housing 120 and to permit rotary motion of the screw shaft 112
relative thereto. The manner in which the support member 124 is sustained
results in the support member 124 being able to bear significant lateral
loadings, in use, transmitting those loadings to the housing 120, whilst
enabling continued operation of the actuator and permitting the support
member 124 to move, angularly, relative to the housing 120.
[0040] A carriage 126 is located externally of the support member 124 and
is able to translate along the support member 124, the carriage 126 being
sustained for sliding movement relative to the support member 124 by ball
or roller bearings 128 conveyed in guide means 130 in the form of
elongate guide grooves formed in the support member 124. To provide
additional stability, the support member 124 is provided with flats 132
with which parts of the carriage 126 can engage to limit angular movement
of the carriage 126 relative to the support member 124.
[0041] The carriage 126 is coupled to the nut 114 such that translational
movement of the nut 114 along the screw shaft 112 is transmitted to the
carriage 126. As the nut 114 is located within the support member 124, in
order to permit movement of the nut 114 to be transmitted to the carriage
126 the support member 124 is provided with one or more elongate slots
134 through which fastener means 136 extend to secure the carriage 126 to
the nut 114. In use, as the screw shaft 112 rotates and the nut 114
translates, the translational movement of the nut 114 is transmitted to
the carriage 126 via the fastener means 136, the fastener means 136
translating along the slot 134 during such movement.
[0042] In order to restrict the ingress of debris into the actuator
arrangement through the slot 134, a sliding seal arrangement 138 is
preferably provided, the sliding seal arrangement 138 including an
elongate seal member 140, a section of which is illustrated in FIGS. 6
and 7. The elongate seal member 140 is secured at its ends to the support
member 124 adjacent the ends of the slot 134, the seal member 140
extending through a seal passage formed in the fastener means 136 such
that a sufficiently good seal is maintained across the slot 134 at all
times whilst permitting movement of the nut 114 and carriage 126.
US60/23111 describes a seal arrangement of a form that may be adapted for
use in this present application.
[0043] An air gap exists between the support member 124 and the nut 114 so
as to ensure that there is no direct contact therebetween that could
result in unfavourable side loads being transmitted to the nut 114, in
use.
[0044] It will be appreciated that the actuator arrangement described
hereinbefore may be used in controlling the operation of an actuator
arrangement of the type described in, for example, British Patent
Application number 0911733.4 with the actuator arm thereof pivotally
mounted to the carriage 126 and the support arm thereof pivotally mounted
to a fixed part of the associated wing structure. The pivot axis about
which the support arm of GB0911733.4 is pivotally mounted would be
orientated relative to the axis of the screw shaft 112 such that these
axes are not perpendicular in either the lateral or wing chord planes, as
described in GB0911733.4. In such an arrangement, rotation of the screw
shaft 112 will result in translational movement of the nut 114 and
carriage 126, the carriage 126 being sustained for such movement relative
to the support member 124 by the bearings 128. The movement of the
carriage 126 results in corresponding movement of the actuator arm. As a
result of the orientation of the axes mentioned above, limited angular
movement of the actuator arm about the axis of the screw shaft 112 takes
place, such movement requiring the carriage 126 to move angularly. The
presence of the bearings 128 and flats 132 prevents significant angular
movement of the carriage 126 relative to the support member 124, and so
the limited angular movement of the actuator arm is transmitted through
the carriage 126 to the support member 124, the movement being permitted
by the sliding bearings upon which the support member 124 is sustained.
[0045] In the arrangement described hereinbefore, the support member 124
is securely sustained or supported by the sliding bearings and so is able
to bear the loadings applied thereto, in use, by the carriage 126 and
actuator arm without impeding the operation of the actuator arrangement.
[0046] It will be appreciated that many of the benefits of the design
illustrated in FIGS. 1 to 5 are also applicable to the embodiment of
FIGS. 6 and 7. For example, the screw shaft 112 can be connected to the
screw shaft of one or more similar actuator arrangements such that a
plurality of actuator arrangements can be driven in synchronism by a
single drive source.
[0047] Each of the arrangements described hereinbefore has the advantage
that the carriage is fully supported, and thus able to react loadings
applied thereto, whilst being able to move axially and translate
angularly relative to its support. Further, each of the arrangements
allows the actuator arrangement to be of compact form, which is
advantageous in that it allows the actuator arrangement to be
accommodated relatively easily within the confined spaced available in
the leading edge structure of a wing.
[0048] It will be appreciated that a wide range of modifications and
alterations may be made to the arrangements described hereinbefore
without departing from the scope of the invention.
* * * * *